Coefficient of Friction

shinnsohai

1. The problem statement, all variables and given/known data
1.a block of mass 5kg moves on a rough horizontal plane with coefficient of friction (Dynamic) 0.2 under the action of a horizontal force of 30N. If the block starts from rest , find the distance it travels in the first 3 second.

2.a particle of mass 6kg,moving at 8m/s on a smooth horizontal surface, goes onto a rough horizontal surface with a coefficient of friction 0.25> Find the distance it moves across the rough surface before coming to rest.

3.This is my own question.Because I might get the concept of friction force wrongly
It's been in my mind for about 3 days thinking of it

A particle moving up a slope with a maintained speed of 1m/s
In another situation a same particle moving up the same slope with a maintained speed of 5m/s

Do the two particle use the same force?

As the Coefficient,mass,gravity,angle of slope are the same


2. Relevant equations
F/N =u(Mew)
F=ma
s=ut+1/2 at^2

Anyhow Regarding the equation,
Relating The Momentum and Force
F=ma
F=m x v/t
Ft=mv

So If The Force is 15N and the object moving at a constant velocity last for 3 seconds
Ft=mv
15(3) = MV
It will be 45 kg m/s ??




3. The attempt at a solution
1.
M=5kg
Force=30N
μDynamic = 0.2
μStatic = F/N (Force Used To Overcome the Static Friction)/(Normal Force)
= 30/(30x9.8)
= 0.1020
Initial Velocity=0
Final Velocity = 0
Time=3 seconds
Distance = Unknown

Untill This Step
What Should I Do With the two different coefficient of friction??

2.
Upon This Stage I Do Realize that I'm Getting Stupiddd

LawrenceC

Static friction is not an issue in this problem. Sum the forces and proceed either by impulse momentum or by Newton's Second Law and velocity-acceleration equation.

LawrenceC

"A particle moving up a slope with a maintained speed of 1m/s
In another situation a same particle moving up the same slope with a maintained speed of 5m/s

Do the two particle use the same force?"

Yes.